Researchers learn more about the possible role of gamma ray bursts on life extinction in the universe

End times. In this drawing, as the shell of gamma radiation (blue) from a gamma-ray burst passes across the Earth, it destroys the ozone layer, leaving life vulnerable to deadly solar ultraviolet radiation. Credit: NASA

(Phys.org)—A pair of astrophysicists studying gamma ray bursts has found that such events might play a much larger role in the existence of life on Earth and other planets than has been thought. In their paper published in the journal Physical Review Letters, Tsvi Piran with the Hebrew University in Israel and Raul Jimenez from the University of Barcelona in Spain, suggest that gamma ray bursts might be responsible for past extinctions on Earth, and for limiting the possibility of life on planets near the center of galaxies.

A gamma ray burst (GRB) is a massive wave of radiation that comes about very quickly due either from a star that is dying or when two neutron stars collide. When the wave strikes another planet it can cause major disruptions.

GRBs come in two varieties, long and short burst. The longer variety are much more common but until recently scientists didn't believe they could occur in our part of the universe at all because it was thought they only occurred in low low-metallicity galaxies. More recently it has been found that though more rare, they do also occur in high-metallicity galaxies like ours. Such findings led the researchers with this new effort to wonder what impact GRBs might have had, or continue to have, on the existence of life on planets, including ours.

Among other things, they found that based on the likely average incidence of GRBs happening close enough, calculations showed a 60 percent likelihood that a GRB has caused an extinction event here on Earth within just the past billion years. They also found that planets are likely to be less impacted by GRBs the farther away from the center of their galaxy they are simply because there are less such events occurring due to the existence of fewer stars in general. They also noted that it appears unlikely any form of life would have been able to survive anywhere in the known universe prior to 5 billion years ago, as galaxies were so compact before then and strikes would have been very common.

The researchers don't believe a GRB striking the Earth could penetrate the atmosphere, but do believe one could destroy the ozone layer, which would of course lead to the extinction of most living things. They believe it's possible that such a strike could be the cause behind the Ordovician extinction, approximately 440 million years ago.

ABSTRACTAs a copious source of gamma rays, a nearby galactic gamma ray burst (GRB) can be a threat to life. Using recent determinations of the rate of GRBs, their luminosity function, and properties of their host galaxies, we estimate the probability that a life-threatening (lethal) GRB would take place. Amongst the different kinds of GRBs, long ones are most dangerous. There is a very good chance (but no certainty) that at least one lethal GRB took place during the past 5 gigayears close enough to Earth as to significantly damage life. There is a 50% chance that such a lethal GRB took place during the last 500×106 years, causing one of the major mass extinction events. Assuming that a similar level of radiation would be lethal to life on other exoplanets hosting life, we explore the potential effects of GRBs to life elsewhere in the Galaxy and the Universe. We find that the probability of a lethal GRB is much larger in the inner Milky Way (95% within a radius of 4 kpc from the galactic center), making it inhospitable to life. Only at the outskirts of the Milky Way, at more than 10 kpc from the galactic center, does this probability drop below 50%. When considering the Universe as a whole, the safest environments for life (similar to the one on Earth) are the lowest density regions in the outskirts of large galaxies, and life can exist in only ≈10% of galaxies. Remarkably, a cosmological constant is essential for such systems to exist. Furthermore, because of both the higher GRB rate and galaxies being smaller, life as it exists on Earth could not take place at z>0.5. Early life forms must have been much more resilient to radiation.

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16 comments

They also noted that it appears unlikely any form of life would have been able to survive anywhere in the known universe prior to 5 billion years ago, as galaxies were so compact before then and strikes would have been very common.

THIS is a very important statement, and it may in fact be the answer to the fermi paradox.

I do not think early life forms were more resilient to radiation, that flies in the face of progressive adaptation each generation. I think the energy was weaker each cycle and progressively allowed life to hold on longer.

5 billion years ago is close to when Earth was formed and life came here soon thereafter. This tells me that life is very easy to start up everywhere where conditions permit. Since conditions permit it in an ever growing range of conditions... therefore life is certain to be everywhere in the universe where it can latch on and survive today.

This report suggests that life is most likely in the suburbs of older galaxies and the time frame is the last 4 - 5 B years. If true, the answer to "where are the aliens" is that there may be far fewer exo-life planets than the exo-planet search suggests might support life. Additionally, frequent extinctions due to GRB increase as distance from the center of a galaxy decreases means that earth may be developmentally ahead of intelligent life elsewhere in our own galaxy. We are near the edge of our galaxy and have had several extinctions, some important ones may have been GRB events.

I was talking about this other day. My supposition is that life is inevitable if the right conditions not only present themselves but if those life forms that do arise can survive multiple catastrophes. I wouldn't be surprised if we find out that Mars is a failed life planet that didn't survive its catastrophe. My question would be, what would have caused Mars to lose most of its atmosphere OR what stopped it from gaining a better atmosphere.

I always wondered for the confidence of someone main stream cosmologists claimed that the Earth is about 5 billion years. Does it happen to them sometimes to think on this issue in greater depth or love to repeat others thoughts read in a textbook or entertainment literature, without subjecting them to experimental and logical verification ? I personally can not find even one evidence that can provide a solid support for such a claim. The probability gamma ray burst to hit the certain planet and destroy alleged life on it is so insignificant that this article makes sense only to remind us that there is such theoretical phenomenon.More logical reason for the lack of signs of intelligent life in the nearest cosmos is that the life does not emerge by chance. But this is heresy for the modern main stream science and so diligent in its stubborn makers will grasp to any absurd ideas or explanations, which not remind to them for the Creator.

Does it happen to them sometimes to think on this issue in greater depth or love to repeat others thoughts read in a textbook or entertainment literature, without subjecting them to experimental and logical verification ?

Since you harbor Creationist beliefs, do you subscribe to the Creator of the Bible? If so I cant understand how you are able to ask this question seriously. Even so, with your belief in your creator, how is it subject to experimental and logical verification?

The science is there for you already but it seems you choose to disbelieve it. If you are asking for evidence, it is there. If you wont accept the evidence, why are you here asking for proof?

Because here come people who understand something of the various fields of science, I shall bring only scientific evidence for creation, though for who that has a heart for truth and harmony in his soul is sufficient only the scriptureas evidence. Modern science in the area of physics, cosmology, chemistry, microbiology, genetics give thousands evidences for creation and expose the myth of evolution without difficulty. Mathematics and theory of programming also helped a lot in this direction, which provide quantitative evaluation for the absurdity of evolution theory. Search for some movie in internet (there are many), which demonstrate the main features in the cells as a synthesis of protein for example, or coping of DNA before replication of the cell, to get the idea for the complex precise synchronized processes in the cell that are needed from the very beginning for it normal function.

I shall bring only scientific evidence for creation, though for who that has a heart for truth and harmony in his soul is sufficient only the scriptureas evidence.

Show me your scientific evidence for creation. It has to include evidence for the creator.

Modern science in the area of physics, cosmology, chemistry, microbiology, genetics give thousands evidences for creation and expose the myth of evolution without difficulty.

Show me your scientific evidence for creation. It has to have a hypothesis for the creator.Show me your scientific evidence for creation. It has to include how to test your hypothesis.Show me your scientific evidence for creation. It has to include what experiments you would run to show a creator exists.Show me your scientific evidence for creation. What data will you have to provide support for your hypothesis?

It seems to me that you are a little nervous and this usually shows uncertainty. Perhaps you have not read the Bible and therefore wander. But even so, you can search for scientific evidence and to find them at every step and in every science that deals with the structure of the world and the interactions of the various systems in it. The lack of basic knowledge about the world we live severely limits the horizons for man and can put him in deep illusions. So you can explore scientific facts honestly and with purely scientific methods to not ask such questions.

Born and raised in a church environment. Went to two services on Sundays, my parents hosted prayer on Monday nights, we were dragged to Wednesday bible study and had to attend youth events on Saturdays. I believed my whole life up until I had doubts when I was 16. As I got older I started to study science, math and history. I even believed in the creation absurdity after catching up on evolution, astrophysics, cosmology and biology and my doubts grew. My study into history finished off religious nonsense and I saw the truth at 24.

I also own two bibles none of which are KJ versions. So yes I have read the bible and was preached at for years.

Answer the questions I presented to you based on your words:

I shall bring only scientific evidence for creation, though for who that has a heart for truth and harmony in his soul

It seems to me that you are a little nervous and this usually shows uncertainty. Perhaps you have not read the Bible and therefore wander. But even so, you can search for scientific evidence and to find them at every step and in every science that deals with the structure of the world and the interactions of the various systems in it. The lack of basic knowledge about the world we live severely limits the horizons for man and can put him in deep illusions. So you can explore scientific facts honestly and with purely scientific methods to not ask such questions.